CVE Intelligence
High Memory corruption

CVE-2026-20434 — Out-of-bounds Write in Mediatek Lr12a

In Modem, there is a possible out of bounds write due to a missing bounds check. This could lead to remote escalation of privilege, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is needed for exploitation. Patch ID: MOLY00782946; Issue ID: MSV-4135.

Published Mar 2, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: MediaTek

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.2% (30-day exploitation probability)+2
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.23%
ahead of 13% of scored CVEs · Oct 15, 2026
Affects
Mediatek
Lr12a and 5 more
CVSS base
7.5
High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Mediatek Lr12a, Mediatek Lr13, Mediatek MediaTek chipset…).
  2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  3. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Mediatek Lr12a versions not specified by the source Vulnerable NIST National Vulnerability Database
Mediatek Lr13 versions not specified by the source Vulnerable NIST National Vulnerability Database
Mediatek MediaTek chipset version MT6980Dversion MT8675version MT8673version MT8668version MT8667version MT8666version MT6991version MT6990
and 86 more version MT6989Tversion MT6989version MT6985Tversion MT6985version MT6983Tversion MT6983version MT8678version MT6980version MT6899version MT6897version MT6896version MT6895TTversion MT6895version MT6893version MT6891version MT6890version MT6889version MT8789version MT8893version MT8883version MT8873version MT8863version MT8798version MT8797version MT8795Tversion MT8793version MT8792version MT8791Tversion MT8791version MT8676version MT8788Eversion MT8788version MT8786version MT8781version MT8771version MT8768version MT8766Rversion MT8766version MT8765version MT8755version MT6885version MT6767version MT6785version MT6783version MT6781version MT6779version MT6771version MT6769Zversion MT6769Tversion MT6769Sversion MT6769Kversion MT6769version MT6768version MT6785Tversion MT6765Tversion MT6765version MT6763version MT6762Mversion MT6762Dversion MT6762version MT6761version MT6739version MT2737version MT2735version MT6873version MT6886version MT6883version MT6880version MT6879version MT6878Mversion MT6878version MT6877TTversion MT6877Tversion MT6877version MT6875Tversion MT6875version MT6855Tversion MT6855version MT6853Tversion MT6853version MT6835Tversion MT6835version MT6833Pversion MT6833version MT6789version MT6785U
Vulnerable CVE Program (cve.org) e CISA ADP
Mediatek Nr15 versions not specified by the source Vulnerable NIST National Vulnerability Database
Mediatek Nr16 versions not specified by the source Vulnerable NIST National Vulnerability Database
Mediatek Nr17 versions not specified by the source Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Adjacent
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
7.5 CVSS 3.1 High 1.6 5.9 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
7.5 CVSS 3.1 High — — CISA-ADP via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 134c704f-9b21-4f2e-91b3-4a467353bcc0)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-787 · Out-of-bounds Write

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.23%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · mediatek, inc./mediatek chipset
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • CVSS changed · 7.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Mar 2, 2026 · MediaTek

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

Elsewhere on this site

Mediatek
every CVE for this vendor
Memory corruption
same class
CWE-787
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-20589 Out-of-bounds Write in Mediatek Mt2718 Firmware 11d
  • CVE-2026-20588 Out-of-bounds Write in Mediatek Mt2718 Firmware 11d
  • CVE-2026-20544 Out-of-bounds Write in Mediatek Mt8910 Firmware 11d
  • CVE-2026-20543 In Modem, there is a possible information disclosure due to a logic error. This could… 11d
  • CVE-2026-20541 In Modem, there is a possible out of bounds read due to a missing permission check. This… 11d
  • CVE-2026-20586 Out-of-bounds Write in Mediatek Mt8910 Firmware 11d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-20434 is "Out-of-bounds Write in Mediatek Lr12a", rated High. It affects Lr12a (Mediatek); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 0.23% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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